$($a$)$ The most important compounds in hardened concrete are called C$-$S$-$H$.$ This stands for?

$($b$)$ Fresh concrete does not "dry" $($though some of the water does evaporate$),$ instead much of

the water is used in a chemical reaction with the Portland cement called hydration to form

C$-$S$-$H$.$ As noted in the PCA guide, to completely react the Portland cement requires a $(\frac{w}{c})$

ratio of at least $0\mathrm{.}22-0\mathrm{.}25.$ However, in the real$-$world, where fresh concrete is not perfectly

mixed and not all cement is able to access$/$find$/$react with sufficient water, a ratio of $0\mathrm{.}4$ is

needed to ensure the reaction can be completed. Therefore:

For $\frac{w}{c}=0$ you have just Portland cement $($duh$)$

For $\frac{w}{c}<mn>0</mn><mn>.</mn><mn>2</mn><mn>2</mn>$ there will be a lot of unhydrated cement, and no unreacted water

For $\frac{w}{c}>0\mathrm{.}4\frac{w}{c}=00\mathrm{.}22$ there will $be$ some unhydrated cement, but still $no$ unreacted

water.

For$\frac{w}{c}>0\mathrm{.}4$ there will $beno$ unhydrated cement, but too much water which will

take $up$ space and reduce strength.

Okay, finally $onto$ your task: Extend the sketch $of$ the "typical curve" back $to\frac{w}{c}=0on$ the

plot below. Note, this comes from the PCA guide, $Ch.1.$